1. Field of the Invention
The present invention relates to a curable resin composition and a cured product made from the resin composition. In particular, the present invention relates to a curable resin composition comprising a polyorganosiloxane and polyimide and to a cured product thereof.
2. Description of the Background Art
Today, semiconductor devices are widely used for various electronic instruments. There are strong demands for miniaturization of semiconductor devices, small energy consumption, high speed, and reliability of semiconductor devices. Decreasing the dielectric constant and increasing heat resistance of the insulating film arranged between wiring layers has been studied as one means for satisfying these various demands.
Materials such as SiOF, organic SOG (Spin on Glass), fluorocarbon polymer, polyimide, polyparaxylylene, and benzocyclobutene polymer, for example, are currently known as materials for low dielectric constant insulating film.
The dielectric constant of these materials is decreased by incorporating a fluorine atom and/or alkyl group in the molecules of the insulating film to decrease the density or to reduce the polarity of the molecule itself. The heat resistance is increased by introducing a siloxane structure, imide bonds, or aromatic rings into the insulating film molecules.
However, among these low dielectric insulating films, films using SiOF, for instance, do not have a sufficiently low dielectric constant as compared with conventional insulating films such as films of silicon oxide which are used for semiconductor devices. The organic materials such as an organic SOG, polyimide resin, polyparaxylylene, and benzocyclobutene polymer, on the other hand, have poor heat resistance and moisture resistance. All these insulating films are thus unsatisfactory as a film with a low dielectric constant.
An alkoxysilane compound is well known as a starting material for producing polysiloxane resins by hydrolysis and the dehydration-condensation reaction following the hydrolysis.
The polysiloxane resins are thermosetting and the cured materials have superior heat resistance and insulating properties. However, if the alkoxysilane compound is used as a starting material, the resin exhibits large volume shrinkage during curing resulting in cured products with cracks. Incorporation of an acrylic resin or the like in the hydrolyzate and/or partial condensate of the alkoxysilane compound have been investigated as a means for preventing cracks during the curing operation. Some examples of such a composition which have been proposed include a composition comprising a partial condensation product of organosilane, a dispersion of colloidal silica, and a silicone-modified acrylic resin (Japanese Patent Application Laid-open No. 135465/1985), a composition comprising a condensate of organosilane, a chelate compound of zirconium alkoxide, and a hydrolyzable silyl group-containing vinyl resin (Japanese Patent Application Laid-open No. 1769/1989), and a composition comprising a partial condensate of organosilane, a hydrolyzable silyl group-containing vinyl resin, a metallic chelate compound, and a .beta.-diketone compound and/or a .beta.-ketoester (Japanese Patent Application Laid-open No. 58824/1992).
However, a problem with these compositions is that the heat resistance inherently possessed by a polysiloxane resin is lost in the cured products produced from these compositions.
A polyimide resin produced from tetracarboxylic acid dianhydride and a diamine compound via a polyamic acid is commonly used as an orientation film for liquid crystals, insulating film for semiconductors, protective coat, adhesive, and the like. Aromatic polyimide resins in particular have superior heat resistance and high strength and are used in applications in which these characteristics are demanded.
However, polyimide resins generally exhibit inferior electrical insulation properties and poor moisture resistance as compared with polysiloxane resins. Because of this, a method for improving a polyimide resin with a polysiloxane resin has been proposed. For example, Japanese Patent Applications Laid-open No. 7437/1983 and No. 13631/1983 disclose a method of using a dimethyl silicon oligomer shown by the formula H.sub.2 N--(CH.sub.2).sub.3 --(Si(CH.sub.3).sub.2 O).sub.m --Si(CH.sub.3).sub.2 --NH.sub.2 (wherein m is an integer from 1-100) as a diamine compound which constitutes a polyimide resin. A problem in such a resin is poor heat resistance. Japanese Patent Applications Laid-open No. 99236/1988 and No. 99536/1988 disclose a method of blending a hydrolysis-condensation product of alkoxysilane and a solution of polyamide acid (specifically, polyamic acid). A drawback to these compositions is poor dispersibility of the polysiloxane component in the polyimide resin in coating films, giving rise to impaired smoothness of the coating films. Japanese Patent Application Laid-open No. 207024/1994 discloses a solution comprising an alkoxysilane hydrolyzed and condensed in a solution of a polyamide acid which possesses a specific-type silyl group. The heat resistance of coating film made from this composition may decrease if a large amount of polysiloxane is used. In addition, the mixed solution of polyamide acid and the hydrolysis-condensation product of alkoxysilane exhibits poor storage stability.
The present invention has been achieved to provide a curable resin composition and cured products overcoming the various above-described problems.